For navigating amongst related objects computer users know a widget of graphical user interface—known as “menu bar”—which allows the users to have point-and-click access to specific functions, such as saving a file, copying text, or opening a help window.
A menu bar is a widget of graphical user interface which is well suited for navigating amongst related objects. Indeed, a menu bar is adapted for displaying groups of objects within respective visually linked display areas. Typically the display areas appear in a rectangular shape, under the menu bar. A menu bar is further adapted, upon user selection of a relation between an object of one group displayed in a previous display area and a further group of objects, for displaying objects of the further group in a further display area visually linked to the previous display area.
However designing widgets of GUI implies at least to pay attention to:                screen encumbrance; that is, to minimize the size of the widget of GUI compared to the workspace on the computer screen, and to        mouse displacement; that is, to minimize the movement of the hand to navigate amongst related object.        
Since, in a classical menu bar, each further group of objects is displayed in a further display area shifted compared to the previous display areas, a menu bar navigation system may suffer from both screen encumbrance and great mouse displacements to navigate amongst the related objects.
It is also known from the man of the art a circular pop-up menu also known as “pie menu”, or “radial menu”, where selection depends on direction, a pie menu being made of several “pie slices”. In this respect, FIGS. 1 and 2 show different examples of pie menus 11, 13.
To use a pie menu, a user usually activates the selection indicator of the pointing device—for example a pen—by pressing down on the screen with the pen during a short interval of time. The pie menu 11 then appears with its centre under the tip of the pen. The user can then highlight an object by keeping the pen pressed and making a stroke towards the desired object. If the object is not related to a group of objects but is related to a command, the command can be run by selecting the object. The object can be selected by lifting the pen. If the object is related to a group of objects and the user stops moving the pen, these objects may be displayed within a ring shaped pattern with its centre under the pen.
Accordingly, as illustrated in FIG. 2, each new group of objects is displayed in a new pie menu 13 shifted compared to the previous pie menus 11.
Consequently pie menus, which are intuitive and easy to use, answer the two concerns of screen encumbrance and great mouse displacements as long as they do not provide sub-menus. The number of displayed objects may also be a problem.
For this reason, pie menus are not indicated to navigate amongst a great number of related objects with a great number of relations between them.
U.S. Pat. No. 5,689,667 discloses a menu system combining a radial marking menu portion with a linear menu portion displayed simultaneously to try to correct the above mentioned gap of pie menus.
The linear portion of the menu system is displayed only if the menu or submenu to be displayed contains more than eight items. In this case, the eight most used items are displayed in the radial menu portion, the other items being displayed in the linear menu portion.
On another hand U.S. Pat. No. 6,414,700 describes a display comprising menu zones arranged in a pattern where a menu is displayed when a zone is activated. The display also comprises menu bars overlapping the zones where a menu is displayed when a menu item is activated. The menu bars are positioned around a central marking zone and are arranged in a stair step pattern. However the menu bars are used like the menu bars that appear at the top of typical windows type interfaces.
However the problems of screen encumbrance and great mouse displacements to navigate amongst the related objects are not solved by the known solution.
Thus, according to the limitations of the existing solutions shortly discussed above, there is a need for an improved widget of graphical user interface for navigating amongst related objects.